The present invention relates to data storage systems. More specifically, the present invention relates to data storage systems using read heads which utilize the giant magnetoresistive (GMR) effect.
Magnetic sensors utilizing the GMR effect, frequently referred to as "spin valve" sensors, are known in the art. A spin valve sensor is typically a sandwiched structure consisting of two ferromagnetic layers separated by a thin non-ferromagnetic layer. One of the ferromagnetic layers is called the "pinned layer" because it is magnetically pinned or oriented in a fixed and unchanging direction by an adjacent antiferromagnet layer, commonly referred to as the "pinning layer," through exchange coupling. The other ferromagnetic layer is called the "free" or "unpinned" layer because the magnetization is allowed to rotate in response to the presence of external magnetic fields.
One type of self pinned layer is known in the art as an artificial antiferromagnet layer (AAF). Such a layer is formed by three layers, a first ferromagnetic layer, a second ferromagnetic layer and a non-magnetic spacer layer separating the two ferromagnetic layers. The two ferromagnetic layers have magnetic vectors which are biased in antiparallel directions and in the plane of the sensor. This is described in, for example, U.S. Pat. No. 5,583,725, issued Dec. 10, 1996 to Coffey et al., entitled "SPIN VALVE MAGNETORESISTIVE SENSOR WITH SELF-PINNED LAMINATED LAYER AND MAGNETIC RECORDING SYSTEM USING THE SENSOR which is incorporated herein by reference.